1. Field of the Invention
The present invention relates generally to the field of orthodontics. More specifically, the present invention discloses a method for producing improved orthodontic aligners.
2. Background of the Invention
Like many areas involving the delivery of healthcare, the field of dentistry is currently involved in a process of rapid change in what has until recently been considered conventional practice. Such changes are taking place in many fields and are often the result of, and are driven by the integration of new computer-based digital technologies, which tend to become the core of powerful new methodologies. In the dental specialty of orthodontics, for example, the process of laser scanning and the three-dimensional imaging of a patient's teeth and then the manipulation of the virtual tooth positions within a computer-aided-design (CAD) environment is an example. Commercial orthodontic service centers have emerged that provide new types of services for orthodontists based on such computer driven three-dimensional imaging methods. These new commercial enterprises, based on three-dimensional imaging and CAD manipulation of tooth positions and tooth relationships have become routinely used by orthodontists and some dentists as part of a successful new “computer perfect” approach to straightening teeth. The integration of these digital services into orthodontics has been commercially successful, and many clinicians feel that utilization of these new 3D imaging-based technologies has led to a higher standard of care.
To use the newly-available digital services, an orthodontist's support staff first takes an impression of a patient's teeth, gums and soft tissue. From the impression, a positive stone model is poured and allowed to cure. Instead of retaining a patient's models for in-office case diagnosis and treatment planning as in the past, the attending orthodontist will instead ship the patient's models to a regional commercial orthodontic service center. A number of services are available to a doctor using such service centers, and these services will be provided according to a prescription and other instructions sent along with the patient's models to the service center.
As is the case in most areas of healthcare, it is not uncommon for the introduction of a central technological improvement to drive a reassessment and revision of what had previously been considered standard and accepted practice. When technology-driven changes occur within a specialized field, some of the conventional procedures routinely used in the past may be rendered unnecessary by the technological innovation and are dropped. Other established procedures however may happen to integrate well with the new technology and are thereby themselves augmented, improved and retained alongside the new practices. The present invention, to be described in full detail below consists of new methods based on a combination of past practices and computer-based three-dimensional imaging and related CAD-based procedures. Stated differently, the present invention can be viewed as being a synthesis of the new digital methods with conventional methods that in combination create an improved methodology for delivering orthodontic therapy.
Andreiko et al. To fully appreciate the advantages of the present invention, consider U.S. Pat. No. 5,139,419 (Andreiko et al). Andreiko et al. disclose a methodology beginning with scanning of a patient's models as described above to produce a digital code that can be assimilated by the computer software. For this step, models can be scanned by any of several current methods to create digital code representing a virtual model of the teeth, gums and soft tissues that can be visually displayed on a computer screen. Andreiko et al. describe methods for the virtual separation of individual teeth from adjacent teeth and soft tissues, and methods for bodily repositioning of individual teeth and groups of teeth.
Generally, Andreiko et al. describe gross movements of groups of teeth establishing or correcting factors such as arch width and arch shape. Next, individual teeth are torqued, tipped, rotated, intruded or extruded and otherwise bodily repositioned according to known standards and established criteria. Next, gnathological fine-tuning of positions of the teeth of one arch relative to the teeth of the other arch is accomplished so the upper and lower teeth will interdigitate in a stable and centric relationship. The purpose of these procedures is to arrive at an ideal post-treatment condition in the form of a finished, virtual model within the CAD software. Andreiko et al. describe methodologies for the use of such digitally-produced results that constitute the operational foundation of the new commercial orthodontic service centers described above, as well as other uses such as the fabrication of customized orthodontic hardware such as archwires and brackets custom-tailored and fabricated for treatment of an individual patient.
Doyle et al. Other developments using digitally-derived treatment objectives can be understood by examining U.S. Pat. Nos. 5,863,198 and 5,879,158 to Doyle et. al. Orthodontists and their staff understand that the accuracy with which orthodontic brackets are positioned on the teeth largely determines the quality of the case when finished, and it is well known that human error is always involved in the process of direct (manual) bonding.
Doyle et al. describe methods for using the output of the digital methodologies to improve the accuracy with which brackets can be placed. From a process that begins similarly to the process described by Andreiko et al., digital output representing the idealized occlusion is used to provide targets for the placement of virtual brackets on the virtual teeth. Once positioned, the resulting three-dimensional CAD surfaces are used to define placement jigs. The digital code representing the virtually-treated ideal occlusion and the virtually-placed brackets is used to drive an industrial machine tool. The industrial machine tool, such as a CNC-driven milling machine is employed by Doyle et al. to form patient-specific and tooth-specific orthodontic bracket placement jigs. These positioning jigs, or “bonding” jigs are used by orthodontists during the bonding step where orthodontic brackets are bonded to each individual tooth. These methods represent another means of transferring a virtually determined “computer-perfect” treatment configuration to the actual oral realities of an individual. These methods and devices take bracket positioning to new levels of bracket placement precision that is beyond what any individual person is capable of using manual methods.
Orometrix®. One of the commercial efforts to bring scanning and three-dimensional imaging technology into orthodontics is known as the Orometrix® program. Orometrix first was structured as a joint venture with a German company that had developed a successful numerically-controlled custom archwire bending machine. That technology was combined into a system including a new type of hand-held oral scanner and a new type of scanning methodology. The commercializing company has been known by several names including Orometrix, Syrinx and Sure Smile. This combination of technologies is covered by a series of patents beginning with U.S. Pat. Nos. 6,315,553 and 6,318,995 to Sachdeva. This system is based on a inter-oral handheld scanning wand connected to a computer with accompanying software. To use the system, an orthodontist holds the working end of the wand in close proximity to the patient's posterior teeth and then the wand is slowly moved forward, around the front of the arch, and then around to the posterior teeth of the other side of the arch. Software associated with the inter-oral scanning wand stitches one frame to the next and in the process, a three-dimensional image of the entire dental arch and gums is created. As can be appreciated, a scanning method as taught by Sachdeva could be used to scan a patient's models in the setting of a commercial orthodontic service center, or more practically, the inter-oral wand could be used at chair side to scan a patient's teeth directly. In such as case, the resulting three-dimensional image obtained from this scanning method could be forwarded to a commercial service center for processing according to the present invention via the internet.
Invisalign®. Yet another example of the orthodontic application of digital technologies is seen in the commercial service known as the Invisalign® program. The Invisalign® program is based on U.S. Pat. No. 5,975,893 (Chishti et al.), and the many related patents, including in particular U.S. Pat. No. 6,398,548 (Muhammad et al.). As with the other approaches described above, the Invisalign program involves the presentation of a patient's virtually-treated finished occlusion. From that, output methodologies are used to fabricate a series progressive polymeric tooth aligners. Such aligners, sometimes called positioners, are generally similar in appearance to appliances known as mouth guards worn by athletes or the soft plastic appliances worn to protect the teeth against the destructive effects of bruxism. The terms “aligner” and “positioner” are can be viewed as being largely synonymous. An example of an Invisalign aligner 20 is shown generally in FIG. 1. The removable aligner 20 has a polymeric shell with a plurality of cavities 24 to receive the patient's teeth 10, as illustrated in FIG. 1(a). The aligner 20 can be used to engage the patient's upper teeth, lower teeth, or a subset of either of these. However, unlike FIGS. 1, 2, and 2(a), conventional Invisalign aligners do not include openings 26 or aligner auxiliaries 30, as will be described in greater detail below.
The Invisalign® program is marketed as a viable alternative to conventional braces-type orthodontics and is referred to during TV commercials as “invisible braces.” The Invisalign tooth aligners are thin, transparent U-shaped plastic appliances formed over patterns or models of the virtual teeth using a combination of vacuum, pressure and heat informally referred to as the “suck down” process and as such, they are considered suck-down appliances. The term “suck down” also is related to the type of dental laboratory machine on which aligners are formed, such as a Biostar-type machine. The Invisalign-type tooth aligners are formed from a thinner material than mouth guard-type appliances. It is a harder but still relatively flexible and somewhat elastic polymeric material similar to polycarbonate (PC). Other materials are sometimes used for certain phases of the Invisalign process.
In order to produce a series of aligners, an Invisalign technician first scans a patient's model as a means to obtain a CAD-manipulatable virtual model of the patient's teeth, gums and soft tissue not unlike Andreiko et al. and Doyle et al. Like the methods taught by Andreiko et al., such a digital model can be displayed and altered using the software tools of a computer aided design (CAD) system. Once the virtual model of the original malocclusion has been established, an Invisalign technician will then undertake steps involving manipulation of the virtual malocclusion ultimately arriving at a finished or ideal occlusion for that patient, similar to the steps taken by Andreiko et al. and Doyle et al. The finished occlusion, even though virtual, is nonetheless consistent with the full repositioning of the occlusion that would result at the end of a successful active treatment phase.
As can be appreciated, after the steps described above are accomplished, an Invisalign technician has two versions of the patient's teeth available within the virtual CAD environment: One of these represents the original malocclusion and the other represents the ideal occlusion that could be expected at the end of successful orthodontic treatment (i.e., the “beginning” and the desired “end” conditions).
It must be noted that the Invisalign technician is not a trained orthodontist. Since the three-dimensional imaging and the corrected case are virtual, they can easily be made available online to the doctor. Using a special viewing and metrix software package provided to the doctor through the internet, the doctor can examine the correctness and precision of the work performed by the Invisalign technician in great detail. The doctor can approve the work performed by the technician, or provide additional instructions to insure that the assumptions of the technician are consistent with the doctor's original treatment plan. In fact, the doctor at one point in the process must provide his formal approval for the process to continue.
After the attending doctor approves the virtual finished occlusion via the internet or other conventional means, the next step in the Invisalign process involves the creation of typically 15 to 25 incremental progressive physical models. Each of these models represents a snap shot of the patient's occlusion at certain stages along his or her treatment sequence between the “beginning” and “end” conditions as described above. To accomplish this, the Invisalign technician will create a virtual “first transition model” that sees a slight repositioning of all or most of the teeth. This first transition model sees some or all of the teeth being subtly moved from their original pre-treatment positions to a virtual first transition position that is in the direction of their intended finished positions. Similarly, a second virtual transition model is created that represents the teeth moved again slightly further in desired directions. The objective of the Invisalign technician is to create the series of progressive models, each biased slightly further than the previous one, each moving the teeth toward their final finished ideal position. A final model will take the teeth from the series of intermediate positions and move them into their final, desired positions.
Once such a series of intermediate models, and a final model are created by the technician, the digital code representing each of the models in the series is directed to operate a type of computer numerically-controlled (CNC) machines, known as rapid prototyping machines. Within the rapid prototyping machines, physical models are grown using one of a group of known processes generally called stereo lithography or 3D printing. The growing step results in the production of a hard, physical duplicate of each of the series of virtual intermediate models and the final model. These are not virtual models. Rather, they are hard, physical models that can be held by hand.
The next step of the Invisalign process sees each of the series of physical models being in turn mounted in suck-down machines where a combination of pressure, heat and vacuum is used to form actual progressive aligners. Each of the series of physical models is used to form a corresponding series of actual aligners. Once the series of progressive aligners are formed and trimmed, they are sequentially labeled, packaged and shipped to the attending orthodontist. The orthodontist then schedules an appointment for the patient, at which time aligner-retaining devices are installed and the aligners and instructions for their use are given to the patient.
The patient will be instructed to begin wearing the first of the series of aligners for a period of time lasting typically two weeks. After that, the first aligner is discarded and the patient transitions to the next aligner of the series and so on.
The aligners serve to urge the patient's teeth to move accordingly. The teeth are progressively biased and urged to move in desired directions toward their predetermined finished positions by the resilience of the polymeric material of the aligners. In response to the gentle but continuous forces delivered by the aligners, certain physiological processes involving the creation and resorbtion of underlying supportive bone are initiated. The net result is the slow orthodontic movement of the roots of the teeth through the underlying bone.
The orthodontist's role in progressive aligner-based treatment is essentially reduced to that of monitoring the physiological response of the teeth and monitoring the patient's level of cooperation with the treatment schedule. In this monitoring mode, however, the attending orthodontist is not required to establish the progressive sequence or otherwise direct the treatment, because the functionality of the aligners and tooth-moving protocol is determined off-site by the Invisalign technician at the orthodontic service center.
Kesling. The Invisalign process involves a treatment modality based on tooth aligners, whose origins can be traced back in time to the positioner-based therapy introduced in the late 1940's by Dr. Peter Kesling. Kesling's positioners used the materials of the day, such as vulcanized rubber. They were generally bulky, one-piece unsightly appliances, as shown for example in U.S. Pat. No. 3,724,075. Later in the 1970's and 1980's, generally based on the research of Japanese orthodontists, thinner aligners came into use where one aligner was directed to the upper arch and a separate one seated on the lower arch. These aligners were cast in pressure pots and were formed by catalyzing medical grade silicone rubber and other similar biocompatible elastomeric materials. More recently, aligners have been formed from thin, relatively hard, but still elastically flexible materials using the suck-down process. These new materials and the suck-down process for forming are used in the Invisalign program for example.
Since the introduction of positioners by Kesling, all aligners that have been used to positively move teeth (as opposed to retaining or holding teeth once ideally positioned) exhibit tooth-accepting female sockets formed in the aligner. Such sockets are sized to accommodate a single, corresponding tooth, but are intentionally slightly out of register with the actual tooth position. To explain the purpose of this out-of-register relationship and how it is achieved, it is important to understand the conventional or “manual” process for producing progressive aligners which is described below.
Before the current integration of computer-based digital fabrication methods were introduced, aligners were fabricated by the orthodontic support laboratories or by in-practice laboratories. The steps used by a laboratory technician in forming a tooth aligner begin as described above with a set of stone models being poured from the patient's impressions. The next step sees a lab technician sawing each tooth away from the stone model and removing the stone material between the teeth. This process, called “resetting the model” sees most if not all of the teeth being similarly cut completely free of the stone model and then reattached to it using a special adhesive material called “sticky wax”.
When resetting a model for the purpose of forming a series of progressive aligners in the laboratory setting, a laboratory technician would first reset the teeth in slightly more desirable positions than the positions that the stone teeth were in prior to cutting them free. Once the teeth are set with sticky wax in slightly more desirable positions, the technician will actually take an impression of the altered model itself in the same manner that impressions are taken from a living patient. From that impression of the altered stone model, a new stone model representing the slightly improved tooth positions will be poured. From that slightly improved stone model, an aligner will be sucked down.
After the first aligner is formed in this manner, the original modified stone model with its teeth reset to slightly more desirable positions is taken and placed in a container of hot water to heat it. Once sufficiently hot, the sticky wax softens, permitting the repositioning of the teeth into yet better and more desirable positions. This second repositioning is performed by the technician using thumb and index finger forces and once completed, yet another impression is taken of the reset model, and another aligner is created from a second stone model of that set-up. Through a third and forth (or more) series of such cycles, laboratory technicians could produce a series of progressive aligners similar to a series of Invisalign aligners, and they can do so without the use of digital computers, 3D imaging and rapid prototyping machines as required by the digital, 3D imaging approaches.
In comparing the digital Invisalign process to the manual methods of producing progressive aligners, it is important to note that the Invisalign process involves the production of a series of progressive aligners that are capable of orthodontically treating a patient from the beginning of treatment completely through to a finished result. In other words, in some cases, the Invisalign process can serve alone as the only treatment modality. Further, with the Invisalign process it is not necessary for any impressions other than the original impression of the patient's malocclusion to be taken. In contrast, a manually-formed series of progressive aligners are usually limited to treating only sub-objectives of a patient's treatment plan. Manually-produced aligners are used for intermediate treatment goals such as phase 1 tooth leveling and alignment, final aesthetic positioning of the teeth near the end of treatment, or for treating cases that have relapsed after the active phase of treatment has ended. It is possible for manually-produced aligners to be used to accomplish a patient's entire treatment from beginning to end like Invisalign aligners do, but such a series of aligners would require that multiple mid-course correction impressions be taken during the course of treatment. Conventional, manually-produced progressive aligners are typically produced in quantities of three to six sets, whereas Invisalign aligners are usually produced in quantities of from 15 to 35 sets.
Hilliard. Considering only aligner-based orthodontic therapy, independently of whether manual or digital production means are used to form them, orthodontists have amassed considerable experience in the use of aligners due to their long-term availability in orthodontics. Importantly, recent years have seen new ways of directing and amplifying the treatment forces aligners generate, as well as new ways of prolonging the duration of such forces have been devised. For example, U.S. Pat. No. 6,293,790, Heated Orthodontic Pliers, (Hilliard) discloses a system of steel dental pliers useful for modifying suck-down polymeric aligners. Commercially known as “Thermo-Pliers”, they represent a series of instruments that are heated to a controlled temperature. Once hot, they are capable of local heat-softening and then thermally flowing the aligner material to form various types of thermo-formed features.
An example of the utility of Thermo-Pliers in augmenting aligner-based therapy involves a common problem faced by orthodontists which is the difficulty encountered in trying to rotate a tooth. Normally, the positional bias of the aligner, referred to above as an out-of-register relationship between the tooth-receiving socket formed in the aligner relative and the actual living tooth will produce force levels that are not fully capable of correcting the position of a tooth in terms of rotation. Rotations, as opposed to torqueing or tipping-type corrections are relatively difficult to achieve using aligners. To augment an aligner's capability to fully correct a tooth in terms of rotation, the attending doctor uses Thermo-Pliers to form an inward-facing bump in the structure of the aligner. Such a thermo-formed bump is positioned relative to a tooth's socket to produce a force vector of maximum mechanical advantage to rotate the tooth. For example, the bump may be placed at the distal, incisal, lingual position relative to a mandibular left lateral and another bump will be located at the mesial, labial incisal location for that tooth. This pair of co-working bumps creates a coupled rotational force that is very effective in rotating that tooth in a labial-mesial direction. A practitioner may allow partial rotational correction to be achieved just by the natural bias of the aligner. Perhaps six weeks later, the remaining correction can be achieved by activating the aligner through the installation of bumps via Thermo-Pliers.
Such bumps serve to focus energy stored in the local region adjacent to the bump as the elevated bump causes a local outward flexing of the aligner material away from the tooth. The bumps gather stored energy from a relatively wide area and impinge that energy onto the tooth at the most desirable locations to amplify the mechanical forces acting on that tooth.
Another one of the Thermo-Pliers series has features formed in its beaks that when heated are capable of forming a hook structure directly in the otherwise featureless material of an aligner's structure adjacent to the soft tissue or in the relatively flat material of the labial side of an incisor. Hooks are used for connecting orthodontic elastics that provide tractive forces between sectioned portions of an aligner (or the aligner and other fixed appliance structure) as needed during treatment. Similarly, other Thermo-Pliers are used to enhance the performance of aligners by installing other heat-formed features.
Orthodontic Aligner Auxiliaries. An entirely new methodology for using aligners is being mastered by orthodontists as the full treatment potential of aligner-based therapy is being revealed. Aligner-based treatment is popular with patients because aligners have several important advantages over conventional braces. Because patients like aligner-based therapy, and because it is effective, orthodontists seek out training and information related to aligner therapy. Along with the use of Thermo-Pliers, other means of amplifying, regulating and extending the corrective force generating capability of aligners are currently being promoted and extolled within the orthodontic profession.
As can be appreciated, the interior or tooth-contacting surfaces of the sockets of aligners completely surround and are in complete intimate physical contact with the tooth corresponding to the socket, as depicted in FIG. 1(a). In order for forces, such as those that are created through the installation of a bump to be effective, the interior surfaces on the opposite side of the socket must somehow be relieved to permit the movement of the tooth in that direction. In other words, an axiom of orthodontically moving teeth proposes that if you push a tooth in a certain direction, it will not move in that direction unless you have first created free space for that tooth to move into. Orthodontists will therefore alter aligners by discretely cutting away material to create such free space, or a window. Such windows can take many forms, but essentially are created by removing aligner material in the direction that the doctor wants the tooth to move. A window will be created, for example, on the labial side of a tooth if a bump is formed on the lingual side. This allows the focused force exerted on the lingual side of the tooth by the bump to not have an equal but opposite opposing force, and thus the tooth will in fact move labially into the window cut out of the aligner on its labial side.
Another example of relieving an aligner in order to tip a tooth inward or outward (known as correction in terms of torque) is this: Assuming a tooth is in its proper bodily position and only requires uprighting for desired orientation, a window can be cut into an aligner in an area limited to the incisal area of the tooth. With the installation of a bump at the incisal edge on the lingual side, the incisal edges of the crown will swing into the relief on the labial. Since in this example, the bulk of the aligner socket still holds the more gingival portions of the tooth in place, the tooth is uprighted without any bodily displacement from its desired position. In this general manner then, orthodontists can create pushing forces on one side of a socket, and discretely relieve the other side of the socket to very accurately tip, torque, rotate and bodily move the roots of teeth through the supporting alveolar bone.
As described above, Thermo-Pliers can form a force-creating bump extending inward into the tooth-accepting socket of an aligner. Just as easily however, an outward-extending bump can be formed which can be referred to as a “bubble”. When forming a bubble, another outwardly extending bubble can be formed overlapping the first. While the Thermo-Pliers are hot, multiple bubbles can be formed near to, or overlapping each other, and in this way an area can be accurately shaped into one larger outward-extending bubble. Such bubbles may serve as an alternative to the window as described above. Bubbles can provide the relief or room for a tooth to move into in response to inwardly extending bumps on the opposite side of an aligner's socket.
Other useful adjuncts to aligner-based therapy have been achieved through the introduction of other aligner auxiliaries that function while installed or attached to the structure of an aligner, as disclosed in the applicant's U.S. Pat. No. 6,702,575, entitled “Orthodontic Aligner Auxiliary System,” issued on Mar. 9, 2004, and incorporated herein by reference. For example, the following are several of the types of aligner auxiliaries that can be used in conjunction with conventional orthodontic aligners:
FIGS. 2 and 2(a) illustrate a simple tack 30 that can be installed in an opening 26 in an aligner 20. To accomplish the installation of a tack 30, a precisely-formed hole 26 of a pre-determined diameter is punched through the material of the aligner 20 using a hole-forming pliers configured to form a hole of a diameter slightly less than the shank 36 of the tack 30. Next, another pliers configured to push the head 32 of the tack 30 through the hole 26 is used. The tack 30 pops into position where it is tightly retained in the aligner 20 in the punched hole 26.
As can be appreciated, locating such a tack within an aligner to realize optimal physiological tooth-moving response is very similar to the effect achieved by installing a bump in an aligner. The use of a separate tack 30 as described however permits the forces delivered to a tooth to be progressively regulated through using a sequential series of progressively longer tacks 30a–30c, as shown in FIGS. 3(a) through 3(c). The shortest tack 30a would be installed in an aligner 20 first. The domed section would reside in the trough portion of the aligner 20 in direct contact with the tooth 10. After a certain degree of tooth movement is accomplished by the short tack 30a, (typically after two to six weeks) a medium-length tack 30b is installed and the short tack 30a is discarded. as the energy stored in the aligner's structure adjacent to the tack is spent through tooth position correction, a longer tack 30c can be installed after the medium tack 30b is similarly spent.
As can be appreciated, a treatment protocol using a series of progressively longer tacks permits patient participation. A doctor may instruct a patient or the patient's parents to install progressively longer tacks in sequence at home, thereby obviating the need and associated cost of an office visit.
The same sort of progressive activation as shown in FIGS. 3(a)–3(c) can be achieved via a series of tacks having a progression of elasticity. FIGS. 4(a)-4(c) show a series of tacks formed of progressively harder elastomeric materials.
Another methodology for regulating or controllably activating the forces that are directed to teeth via aligner auxiliary devices 30 that are installed directly in an aligner's structure is shown in FIGS. 5 and 6. Like tacks, they first require the punching of a hole 26 through the aligner 20. Such a hole 26 is pre-sized to inter-work with the male threads 38 of the aligner auxiliaries 30. In a sense, such devices can be considered to be self-threading or self-tapping as they screw into the aligner's hard but somewhat elastic material.
Similar to the threaded devices shown in FIGS. 5 and 6, the aligner auxiliary 30 shown in FIG. 7 requires a nut 40 to be installed directly into the opening 26 of the aligner 20. Note that instead of a round hole, the assembly shown in FIG. 7 requires a square or rectangular hole 26 of a predetermined size to be installed in an aligner 20. Such a hole can be formed in an aligner using a special square or rectangular die-punch pliers. The non-round configuration of the hole 26 prevents the nut 40 from rotating as the screw portion 42 is turned.
Tacks 30a and 30b can be used in combination to create a rotational couple as illustrated in FIGS. 8 and 8(a). As can be seen, positioning two aligner auxiliaries 30a and 30b relative to a mal-rotated tooth 10 serve to create a mechanical couple ideally tailored to rotate the tooth 10.
A tack 30 can serve as an anchor or hook for the attachment of latex or urethane elastomeric bands 52, as shown in FIG. 9. As such, its function is not involved in directly contacting a tooth to move it. The tractive forces produced by an elastic band 52 attached in this manner can serve to pull separate portions of an aligner together, or to pull the entire aligner, and the teeth contained in it collectively in one direction. Importantly, note that the tack 30 must engage holes pierced through an aligner, but if their inwardly extending portions contact the underlying tooth, undesirable uncontrolled tooth movement can occur. To prevent contact with the tooth, such devices are typically installed in an outset 28 formed in the aligner 20, as depicted in FIGS. 13(a) and 13(b). An outset 28 is a raised land or plateau that is formed outward, away from the teeth. The hole 26 formed through the aligner 20 that serves to retain the aligner auxiliary 30 is located at the center of the raised land 28 thereby allowing the aligner auxiliary 30 to be retained in the aligner 20, but importantly, held clear of the underlying tooth surface by the height of the land 28.
A plurality of tacks can be employed in combination with elastic bands to move multiple teeth or groups of teeth. As shown in FIG. 10, two tacks 30a and 30b have an elastic 52 stretched between the tacks. Such a configuration would require that the aligner first be partially or completely cut into two pieces 20a and 20b, and then the elastic 52 would serve to draw two groups of teeth together, performing a function known as space closing. Note, both aligner auxiliaries 30a and 30b would typically be attached to the aligner on outsets lest the tips of the tacks undesirably contact the teeth.
Outset tacks can be used to move multiple teeth or groups of teeth apart expansively with a compression coil spring 54. As shown in FIG. 11, the assembly spans to two sections of an aligner 20a and 20b that has been cut into two pieces. This assembly serves to drive the sections apart as well as the teeth contained in each section. Alternatively, an expansion jack screw 50 can be used to move multiple teeth or groups of teeth apart expansively, as shown in FIG. 12. Note that like the outset tacks 30a and 30b described above, the aligner auxiliaries that pop through the aligner are typically held clear of the underlying tooth surfaces by being installed in holes formed in outset or raised lands.
The aligner auxiliaries shown in FIGS. 9–12 are attached to aligners in cases where treatment require that the aligner be cut into two sections. These devices are employed to achieve relative movement between the two sections and in the process, move the teeth they control along with them. Such attachment means however are not limited to tractive or repellant forces between two sections of the same aligner. It should be understood that aligner auxiliaries could include a wide variety of devices intended to handle or generate forces directed to an aligner normally worn by a patient, or to handle extra-oral forces. For example, aligner auxiliaries can be used to handle forces directed to the patient's other arch. This type of device is held in position by an upper aligner located adjacent to the upper first molar. A similar attachment means is incorporated into the lower aligner. A bite jumper spring is compressed between these upper and lower attachments. Aligner auxiliaries can also be used to accept extra-oral devices such as face bows, lip bumpers and the like.
Tacks 30 can be placed to retain the entire orthodontic appliance relative to the patient's teeth and oral anatomy, as shown in FIG. 14. The retaining tacks 30 can be located and installed through holes 26 near the gingival margin between two teeth 10, just distal of the cupids. Another location for retentive tack is interproximal to the first molar and second bicuspid, but they can be installed at any other point determined appropriate by the CAD technician. Retentive tacks project inward from the buccal or labial, or outward from the lingual into the gingival interproximal area and act as clasps of sorts, ensuring the entire aligner 20 remains fully seated on all of the teeth 10 when in the mouth. Since the aligner 20 is generally resilient and somewhat flexible, as the aligner 20 is pushed downward on the teeth 10 into a seated position, the aligner 20 will flex outward along with the retaining tacks. Once fully seated, the resilience of the material will cause the aligner 20 to return to its original shape, thus urging the points of the retaining tacks 30 into gingival interproximal spaces. This relationship provides a gentle retentive lock serving to hold the aligner 20 in place.
Aligner auxiliaries can also serve a decorative function to enable patient self-expression, which a practitioner may encourage as part of a scheme to gain patient cooperation. Patient cooperation is vital for a successful finished orthodontic result. The devices 60 shown in FIGS. 15(a) and 15(b) serve no particular physiological function other than providing a patient with a means of self-expression. Such things can serve to add an element of fun and a vehicle for personal expression to orthodontic treatment for young patients, with the goal again being that of gaining of patient cooperation.